Telephone system



March 3, 1942.Y J. wlcKs TELEPHONE SYSTEM Filed June 30, 1939 2Sheets-Sheet l QQ @QQ NQ w: @v

mmf

QOBONJMW ...O.`l OMZZO o QOLOW 4mm INVENTOR.

J 0H N w|c K.s

ATTORNEYS.

March 3, 1942. J, wlcKs TELEPHONE SYSTEM 2 Sheets-Sheet `2 Filed June3o, 1959 w EN c N @QN E @Q83 x USN 6N .m6 Qwl m f UY E 6.52 @Q M NQQN D@QN NW @uw r IIIIIIIIIII I1 l I||||l IIIIIIJ QN QN NN mw n TSW w @wlw@www www# W% Ind @SN SNITI.. www wl .SN im www. www. EN QMNSOQ @N m HNNN OWN l @mw DNN OOM @QN @QN t, www l n www Rfo www www .M .NEN www2*BNSNUL. Et L i M2314 JF@ EINRUI @Q Sw @WJ f EN Q om ATTORNEYS.

Patented Mar. 3, 1942 UNITE TELEPHONE SYSTEM .lohn Wicks, Oak Park,Ill., assignor to Associatedy Electric Laboratories, Inc., Chicago,Ill., a corporation of Delaware Application June 30, 1939, Serial No.282,006

19 Claims.

The present invention relates to automatic telephone systems and has forone of its objects the provision of improved apparatus for automaticallyforwarding calls intended for a first substation of an automatictelephone system to another substation selected by the subscriber orparty for whose service the first substation is provided.

It is another object of the invention to provide in an automatictelephone system, improved call forwarding apparatus of the characterdescribed which is economical to manufacture and install, is adapted foruse in conjunction with automatic switching apparatus of substantiallyall types, and is thoroughly reliable in operation.

It is another object of the invention to provide in an automatictelephone system, improved call forwarding apparatus of the characterdescribed which is normally inactive and is automatically renderedoperative to respond to calls incoming to the associated substationthrough operation of the apparatus to select a substation to which thecalls are to be forwarded.

It is another object of the invention to provide in an automatictelephone system, call forwarding apparatus of the character describedwhich is arranged in an improved manner such that no auxiliary lines arerequired between the automatic switching apparatus of the system and thesubstation with which the call forwarding apparatus is associated.

It is a further object of the invention to provide in an automatictelephone system, improved call forwarding apparatus which is soarranged that alternating current pulsing over the line extending to thesubstation with which the apparatus is associated, is utilized fordirectively controlling the automatic switching apparatus through whichthe calls are forwarded; thus eliminating the necessity of providing anauxiliary line between the substation and the automatic switchingapparatus of the system.

'Ihe invention is illustrated in its embodiment in an automatictelephone system which comprises a. plurality of substations andautomatic switching apparatus including non-numerical and impulseresponsive numerical switches for setting up connections between thelines extending to the substations. Two embodiments of the invention areillustrated. In each modification, call forwarding apparatus is providedindividual to the lines arranged for call forwarding service. Thisapparatus includes a motor-driven, cyclically operative device which isoperative to transmit to the automatic switching apparatus the impulsesof the directory number designating the substation to which the callsare to be forwarded. This device includes a plurality of controlelements individually corresponding to the substations to which callsmay be forwarded, a station selecting element having a normal positionand operative to off-normal positions individually corresponding to thecontrol elements, and pulsing means adapted to be controlled by any oneof the control elements for transmitting to the automatic switchingapparatus the impulses of the directory number designating thesubstation corresponding to the off-normal position occupied by thestation selecting element. For the purpose of initiating the operationof the call forwarding apparatus, `there is provided a relay which isadapted to be connected to the line arranged for call forwarding serviceand to respond to ringing current transmitted over the line. connectthis relay toV respond to ringing current transmitted over the line,there is provided switching means operative in response to operation ofthe selecting element to any one of its off-normal positions. This relayfunctions -to complete the operating circuit for the motor which drivesthe cyclically operative pulsingfdevice, and the arrangement is suchthat the pulsing device is caused to operate through repeated cycles,thereby repeatedly .to forward an incoming call to theassociated linethrough the automatic switching apparatus to the substation selected forcall transfer, until the call is aban` doned or is answered at thelast-mentioned substation. =In order to arrest the operation of thedevice and to terminate the transmission of ringing current over theline associated with the call forwarding apparatus there is provided inthis apparatus means operative to perform the indicated functions whenthe forwarded call is answered at the substation to which the call isrouted.

In one embodiment of the invention, the irnpulses produced throughoperation of the call forwarding apparatus are transmitted from theassociated substation to the automatic switching apparatus of the systemover an auxiliary line extending between the substation and the auto-VIn the second emmatic switching apparatus. bodiment of the invention,the use of an auxiliary line is not necessary; the call forwardingapparatus provided at the substation arranged for call forwardingservice including means automatically operative in responsive to thepresence of an incoming call on the line extending to the substation fortransmitting alternating current for call forwardingservice functions tocontrol means for transmitting over the associated line a In order to`Further features of the invention pertain to the particular arrangementof the circuit elements described hereinafter, whereby the above andadditional operating features are attained.

The novel features belieted to be characteristic of the invention areser. forth with parue- L ularityA in the appended claims. The invention,both as to its organization and method of operation, together withfurther objects and advantages thereof will best be understoodbyreference-to. the specication taken in connection with theaccompanying drawings in which Figure l illustrates one embodiment ofthe improved call. forwarding apparatus and Fig. 2 illustrates a secondembodiment of the improved` call forwarding apparatus; these twoembodiments of y.;

the invention being respectively associated with two differentsubscribers lines forming a part of the same automatic telephone system.

Briefly described, the system illustrated inthe drawings comprisesavplurality of substations r t A, B, C and D individually associatedzwithlines l, Ii, l2, and I3 in the. order named; which lines all extend tothe automaticswitching apparatus provided in the lineterminatingexchange. This apparatus comprises line rswitches M, I5, itand Ilindividually associated with the lines t3, H, I2 and I3, a plurality ofimpulse responsive selector switches including the two switches. indi--cated at I8 and l5, and a. plurality of impulse responsive connectorswitchestwo of which are indicated at 2Q and 2l, respectively. Thesystem further comprises calllforwarding apparatus individuallyassociated with thesubstations B and D, respectively. The arrangement ofthis apparatus as provided in conjunction with the substation B is suchthat an auxiliaryA line 22 extending from this substation to theautomatic switching apparatus of the line. terminating exchange andanauxiliary line switch 22,3 for serving the line 22are required. Thecallrorwarding apparatus illustrated in Fig.y 2, inassociation with thesubstation D, onthe other hand, is Vsuch that no auxiliary lineextending from this substation to the automatic switching apparatus ofthe line terminating exchange is required. This apparatus does, however,require the provision of an auxiliary line switch Ziiwhich functions toforward calls to the selector switches of the system.

The line switches l, l5, it, V, 23 and 2'4 are f This :rc-lay isarranged to fdl cordance with impulses transmitted thereto, to performline group, subgroup and particular line selecting operations.Preferably, these switches are of the well-known Strowger type, eachhaving embodied therein a Strowger switching mech- ,anism utilizingvertical and rotary motions in its Voperation to select an outgoingline.

Obviously,

Y the control apparatus embodied in the selector and connector switchesis different in each instance depending upon the particular character ofthe switch.

Neglecting for the present the arrangement of the call forwardingapparatus provided in association with the substations B and D, thesystem as described above is entirely conventional in form and its modeof operation is well understood in thel art. Briey described, if asubscriber at the substation A, for example, initiates a call intendedfor the substation. B- by removing the receiver provided at thesubstation A- from its supporting hook or cradley a calling loop circuitis completed by way of the line i!! for initiating the operation of theline switch M. This line switch responds to the completion of thecalling loop circuit by operating toselect a trunk line extending to anidle one of therst selector switches. If the selector switch t8, is thefirst available idle selector switch accessible tor the line switch I4,the last-mentioned@ switch, upon testing the conditionof the trunk lineextending to the selector switch i8 and. finding this line to be idle,operates to extend` the calling loop circuit to the selector switch. Thecontrol apparatus of the seized selector switch i8 now op.- erates to.return the usual dial tone signal to the calling subscriber. Theselector switch I8 responds to the impulses of the iirst digit dialed atthe substation A by elevating its wipers to a position opposite thelevel o bank contacts terminating the trunk lines extending to the con.-nector switches having access to the called line IlY and forming thegroup including the switch 2i). Further, the control` apparatus of theselector switch operates to terminate the dial tone signal. During theinterdigit pause between the first and second digits, the wipers of theselector switch I8 are rotated` step-by-step in the usual manner,successively to.test the condition of the trunk lines respectivelyextending to the connectorY switches of the selected group. If thecon.-nector switchv 2u is the rst available idle switch of the selectedgroup, the rotary movement of the wipers embodied in the selectorswitchv I8 is arrested when these wipers engage the contacts terminatingthe conductors of the trunk line incoming to this connector switch. Inaddition, the control apparatus of the selector switch I8 functions toextend the, calling, loopcircuit to the seized-connector'switch 2&2' Theconnector switchli responds to. they impulsesof ythe second digit dialedatthe calling substation by, elevat.- ingits wipers to a positionoppositethe level of bank contacts terminating the grouplofv linesincluding theV calledline H. In response to the impulses ofathe thirddigit dialed at the calling substation these wipersare rotated intoengagement with the particular set oi' bank contacts apparatus embodiedin thek connector switch` 2l) functions to determinethe idle or busy.condition 'of the selected line'and'to transmitthe usual 'busy tonesignal over the calling loop circuit to the calling subscriber in theevent. the called Aune is busy. rf the called une is found to be idle,'the control equipment embodied in the connector switch functions totransmit ringing current over the called line for the purpose ofenergizing the ringer conventionally provided at the called substation Band over the calling line to inform the calling party that the calledsubstation is being rung. When the call is answered at the calledsubstation a direct current bridge is connected across the conductors ofthe line thereby to complete a circuit for energizing the ring cut-offrelay conventionally embodied in the Control equipment of the operatedconnector switch. This relay, upon operating, functions to terminate theringing operation, to arrest the ringback tone signal and to completethe desired conversational circuit between the calling and calledsubstations. When the ring cut-off relay operates, a loop circuit isestablished between the connector switch 2o and the substation B, whichloop circuit extends through the windings of the 'back bridge or batteryreversing relay conventionally embodied in the connector switch 2t. Theresulting operation of this back bridge relay causes the direction ofcurrent flow over the calling loop circuit to be reversed in the usualmanner, and this current reversal may be utilized for various controlfunctions such as call metering or the like. The manner in which theconnection is released depends upon the particular arrangement of thecontrol apparatus embodied in the connector switch 2B. For example, thisapparatus may be so arranged that the operated switch train is releasedonly when the connection is released at both the calling and calledsubstations. Alternatively, the control apparatus of the connectorswitch may be so arranged that the release of the switch train isentirely under the control of the calling subscriber. Assuming that thelatter arrangement is employed, when the calling party replaces thereceiver provided at the substation A upon its supporting hook or cradlethe calling loop circuit is interrupted with the result that theconnector switch 2|), the selector switch I8 and the line switch |11 aresuccessively released in the order named and in a manner well understoodin the art. When these switches are all restored to normal, the callingand called lines Hi and I are marked as idle in the connector switcheshaving access thereto and the apparatus utilized in completing theconnection is rendered available for further use. In view of theforegoing description it is believed that the manner in whichconnections may be established between the other substations of thesystem will be clearly apparent without further explanation.

Referring now more particularly to the ernbodiment of the callforwarding apparatus illustrated in Fig. l in association with thesubstation B, this apparatus comprises a cyclically operative controldevice which includes a plurality of control elernents or camsindividually corresponding to the substations to which calls incoming tothe line may be forwarded. One such cam is indicated at |60, this camindividually corresponding to the substation C associated with thesubscribers-line l2. Each of the control elements or cams is notchedaround its periphery to provide a camming surface for controlling a pairof impulse shunting springs lol, these springs being transverselymovable with respect to the cams to engage the peripheral surface of aselected one thereof in unison with a station selecting element H32 asindicated by the dotted unicontrol line U. The station selecting element|02 is provided with a pointer portion arranged to cooperate with anindex |93 which includes indices identifying the substationcorresponding to the position occupied by the shunt springs Ill Moreparticularly, the station selecting element |02 is provided with anormal position and a plurality of off-normal positions individuallycorresponding to the substations to which the calls may be forwarded.This element is arranged to control a pair of switching springs I in amanner such that the springs are disengaged when the station selectingelement occupies its normal position and are moved into engagement whenthisv element is operated to any one of its off-normal positions. Thecontrol device further comprises an impulsing cam |05 which is arrangedto operate a pair of pulsing springs |06. Two additional controlelements or cams |01 and |03 are provided, which elements are arrangedrespectively to control the springs embodied in associated spring pilesm9 and For the purpose of driving the enumerated control cams there isprovided a small synchronous motor of the self-starting type which isarranged to be energized from the usual commercial frequency voltsource. More particularly, this motor is arranged to drive a shaft H2upon which the control elements |61 and IUS are mounted at a reducedspeed through a speed reducing mechanism H3. The shaft ||2 is, in turn,geared to drivea shaft Hd upon which the station selecting controlelements are mount-v ed through a second speed reducing gear train- ||5.The shaft ||4 is arranged to drive a third shaft ||5 which carries thepulsing cam |65 through a speed increasing gear train It. Since thecontrol cams H31 and |68 are mounted upon the same shaft, these cams areobviously operated in unison, preferably at a speed of approximately oneand two-thirds revolutions per minute. The gear ratio of the gear trainl5 is such that the station selecting cams carried by the shaft ||4 arerotated three revolutions for each revolution of the cams |01 and m6,'or at a speed of approximately five revolutions per minute. The gearratio of the train l 6 is such that the impulsing cam |65 is driven at aspeed of approximately six hundred revolutions per minute, correspondingto an impulsing rate of approximately ten impulses per second. Ifdesired, the mechanical construction of the portion of the controldevice comprising the station selecting cams, the gear train H6, thepulsing cam |05 yand the station selecting element H32 may besubstantially similar to that disclosed in the copending application ofHans Sengebusch, Serial No. 147,831, filed June 12, 1937.

For the purpose of initiating the operation of the control device thereis provided an alternating current relay |26 which includes a windingadapted to be bridged across the conductors of the line in series with acondenser |22 in response to loperation of the station selecting element|92 to one of its off-normal positions so that it will respond toringing current transmitted over this line. The line connectingequipment of the call forwarding apparatus includes a repeating coil|23, having a pair of windings |24; and |25 adapted to be connected inseries circuit relationship with the condenser |22 and the winding ofthe relay |25) across the conductors of the line and a second pair ofwindings |26 and |21 adapted to be included in a calling loop circuitincluding the auxiliary line 22 and extending to the line switch 23. Thecompletion of a talking circuit between the lines I and 22 is under thecontrol of a polarized back bridged relay |30 which is preferably of thepermanent magnet type.

Referring now more particularly to the operation of the call forwardingapparatus illustrated in Fig. l, it will be apparent that with thestation selecting element |02 occupying its normal position such thatthe contact springs |04 are disengaged, the series path including thewindings |24 and |25 of the repeating coil |23 and the winding of thestart relay is not connected across the conductors of the lineAccordingly, calls incoming to the substation B and routed through theautomatic switching apparatus terminating exchange in the mannerpreviously explained, may be completed and released without in any wayaffecting the call forwarding arrangement. Also, calls originating atthe substation B may be completed without interference occasioned by theassociated call forwarding apparatus. In order to condition the callforwarding apparatus to operate in response to calls incoming to theline II, the station seposition the shunt springs |0| to be controlledby the station selecting cam |00. Immediately the element |02 isoperated to an off-normal position, the springs |04 are closed toconnect across the conductors of the line the series path including thewinding of the relay |20.

With the apparatus in this condition if a call intended for thesubstation B is routed to the line II through the switches I4, I8 and 20from the substation A in the manner previously described, ringingcurrent is projected over the line I I following the operation of thecontrol apparatus of the connector switch 20 to ascertain the idlecondition of the line I I. A portion of the ringing current traversesthe winding of the relay |20 over a circuit which may partially betraced as extending by way of the line conductor I Ia, the contactsprings |04, the winding |24, the winding of the relay |20, thecondenser |22, the winding I and the line conductor IIb. Each time therelay |20 is energized by current traversing this circuit it operates tocomplete, at its armature |2I, a circuit for energizing the synchronousmotor III, this circuit extending from one terminal of the alternatingcurrent source, through the windings of the motor I I I, the armature|33 and the armature I2I to the opposite terminal of the current source.When energized over this circuit, operation of the motor III to drivethe Various control cams, previously described, is initiated. During theinitial operation of the motor, the cam |01 is moved off-normal tooperate the contact springs |34 and |35 respectively into engagement. Atthe contact springs |35 an auxiliary or second circuit is compieted forenergizing the motor III, this second circuit extending from oneterminal of the current supply source through the windings of the motorIII and by way of the contact springs |35 to the opposite terminal ofthe current source. Thus, operation of the motor III is maintainedindependently of the energized or deenergized condition of the startrelay |20 until the control device driven thereby has been operatedthrough a complete cycle of operation. When the contact springs |34 aremoved into engagement a calling loop circuit extending to the lineswitch 23 is completed, this loop circuit extending by way of the lineconductor 22a, the repeater winding |26, the winding of the relay I 30,the repeater winding |2'I, the contact springs |34, |36 and |38 and theopposite line conductor 221i. The direction of current flow over thisloop circuit is such that the polarized relay |30 does not operate; thisrelay being so poled that it only operates in response to the reversalof current flow over the calling loop circuit which occurs when the callis answered at the substation to which the call is forwarded. When theabove-traced calling loop circuit is completed, the line switch 23operates to select an idle one of the selector switches, such, forexample, as the switch I9, to which is has access. When this switch isselected, the calling loop circuit is extended thereto and the selectedswitch is conditioned to respond to the first series of impulsestransmitted over the line 22 through operation of the pulsing springs|03 as controlled by the shunt springs IilI. In order to provide ampletime for the line switch 23 to perform its switch selecting operation,the transmission of impulses from the control device is delayed for apredetermined time interval after operation thereof is initiated. Tothis end, the springs |36 and |38, controlled by the cam |03, are heldin engagement to shortcircuit the springs |0I and |06 until the cam E00has been rotated through 'an angle of approximately 45 degrees. It willbe understood that during such rotation of the cam |0| the stationselecting cams, including the cam |00, are rotated through an angle ofapproximately 35 degrees since the speed ratio between the shafts I4 andI I2 is approximately three to one. By virtue of this arrangement,transmission of switch control pulses from the control device is delayedfor an interval of approximately four and one-half seconds after thecalling loop circuit is completed, this interval being ample for theline switch 23 to test the idle or busy condition of all of the selectorswitches to which it has access. At the end of this interval, the camfollower portion of the spring |38 drops into the notch I08a provided inthe peripheral surface of the cam |00. As a result, the springs |36 and38 are disengaged and the springs |36 and |31 are moved into engagement.Thus the parallel connected shunt springs II and the pulsing springs 05are effectively included in the calling loop circuit. Shortly followingthis operation, the cam follower portion of the shunt spring I0|a dropsinto the notch |0011, formed in the peripheral surface of the stationselecting cam |00. Thus, the shunt springs |0Ia and IIlIb` aredisengaged so that the puising springs |06 are actively included in thecalling loop circuit to transmit thereover to the selector switch I9 theimpulses of the rst digit of the directory number designating thesubstation C. In this regard, it will be apparent that the number ofimpulses transmitted during the digit is determined by thecircumferential length of the notch |00a formed in the peripheralsurface of the element of the cam |00. For example, if the directorynumber designating the substation C is 352, the length of the notch I00awill be so proportioned relative to the pulsing rate and the speed ofrotation of the cam |00 that three impulses are www@ transmitted overthe calling loop circuit during i the interval when the cam followerportion of the spring Ila, is engaging the peripheral surface of the camIBD defined by this notch. In a similar manner, the length of the secondnotch |0019 corresponding to the second digit of the directory numberdesignating the substation C is formed of a length such that fiveimpulses will be transmitted over the calling loop circuit while the camfollower portion of the spring ||||ar is engaging the peripheral surfacedened by this second notch. Also, the length of the notch |000 whichdetermines the number of impulses of the third digit is such that twoimpulses are transmitted over the calling loop circuit by the pulsingsprings |06 during the interval when the cam follower portion of thespring |0|a is engaging the peripheral surface of the cam |00 defined bythis third notch.

The selector switch I9 responds to kthe impulses of the first digit byelevating its wipers to a position opposite the level of bank contactsterminating the conductors of the trunk lines respectively extending tothe connector switches having access to the called line I2. When the camfollower portionrof the shunt spring lilla engages the projectionseparating the notch Milla and lllb of the cam |661, it is moved intoengagement with the associated spring lb to complete an obvious path inshunt with the pulsing springs |06 so that the latter springs are nolonger actively included in the calling loop circuit. Thecircumferential length of the projection separating the two notches|000, and Ib determines the duration of the interdigit pause between thefirst and second digits of -the directory number designating thesubstation C. During this pause,

the wipers of the selector switch |9 are rotated.

step-by-step until a trunk line extending to an idle one of theconnector switches of the selected group is found. Assuming, forexample, that the connector switch 2| is the first available idle switchof the selected group, the selector switch i!! seizes this connectorswitch and extends the callingV loop circuit thereto. Thereafter, andwhen the cam follower portion of the shunt spring Illia drops into thenotch ltliib of the cam |00, the pulsing springs |06 are again activelyincluded in the calling loop circuit so that the impulses of the seconddigit are transmitted to the connector switch 2|. The indicatedconnector switch responds to the impulses of this digit by elevating itswipers to a position opposite the level of bank contacts terminating theten subscribers linesforming the subgroup including the line I2. Whenthe cam follower portion of the spring ||l|a engages the projectionseparating thenotches limb and llc, the shunt springs are again movedinto engagement to short circuit the pulsing springs |65, thereby toterminate the impulses of the second digit and to provide an interdigitpause .during which the control apparatus of the connector switch 2| isconditioned to respond `to the impulses making up the third digit of thedirectory number desig` hating the substation C. The impulses of thisthird digit are started when the cam follower portion of the spring |t|adrops into the notch iililc so that this spring is disengaged from itsassociated spring itil). The connector switch 2| responds to theimpulses of the third digit by operating to select the line l2 from theselected subgroup of lines. The pulses of the third and nal digit areterminated when the cam follower portion of the spring |l||a is movedout of the notch |0|lc and into engagement with its assocated spring|0|b to shortA circuit the pulsing springs |05. Shortly following theendof thethird digit, the cam follower portion of the contact spring |38moves over the trailing edge of the notch Ia provided in the cam |8 sothat the springs |36 and |38 are moved into engagement, following which,the springs |36 and |31 are disengaged. T hus, the shunt springs IDI andthe pulsing `springs |06 are effectively shunted from the calling loopcircuit so that no further impulses may be transmitted thereover untilasecond cycle of operation of the control device is initiated. After theAimpulse transmission is ended, the calling loop circuit is notinterrupted for a substantial time interval during which the called line|2 is tested to' determine the idleor busy condition thereof, ringingcurrent may be transmitted overthe line to energize the signal deviceprovided at the called substation and the call may be` answered. Thus,the cams |01 and |08 are rotated through an angle of approximately 135degrees during the interval when the call is being forwarded through theswitches l I5, I9 and 2| to the called line I2. These cams must berotated through an additional angle of 225 degrees lbefore they arereturned to their respective normal positions to `complete theroperatingcycle.` Thus, aV period of approximatelyA twenty-fourv seconds isprovided during which the called substationmay be signaled and the callanswered.

Assuming that the called line i2 is idle at thel time it is selected bythe connector switch 2| and,

f further, that the call -is answered during thel above-mentioned timeinterval required for the control device to complete its cycle ofoperation, the ring cut-off relay provided in the connector switch2|operates to complete aloop circuit extending through thewindings of theback bridge relay of this switch andincluding the conductorsof thecalled line l2 in the usual manner. Upon operating, the back bridgelrelay of the connector switch functions to reverse' the direction ofcurrent flow over the loop -circuit extending from the connector switch2| to the repeater |23. As a result, the polarized relay |30 is'causedto operate. Upon operating, the relay |30 opens, at its armature |33, a.point in ,the initiallyco1`n pleted circuit for energizing the motor`At t its armature |32, the relay |30 completes .an obvious path forshort-circuiting the condenser |22-, thereby to establish av directcurrent bridge across the conductors of the line ||.v More par` 5ticularly, a loop circuit is established which extends by way of theconductor Ha, the springs |06, the winding |24, the 4winding of therelay |20, the armature |32, the winding |25 andthe opposite lineconductor lib.` When this circuit is completed, the ring cut-off andback bridge relays embodied in the. connector switch 20 are causedsequentially to operate in the manner previously explained so that theringing operation of the connector switch 2o is arrested and atalkingcircuit is yestablished which includes "the re-rk peating coil|23 and extends from the calling sub,- station A to the substation C.

At its armature |3I, the back bridge relay i3d, upon operating,effectively shunts the contact springs |34 from" the loop circuitincluding the line 2 2. As aI result', this loop circuit is notinterrupted when the control cams |01 and |08,

are returned to their respective home positions to end the operatingcycle of the `control device. When the cams |01 and IUS are rotated backto normal, the cam follower portion of the'lower control spring |35drops into the notch provided in the peripheral surface of the cam |01so that the springs |34 andf|35 are respectively disengaged. When thesprings |35 are'moved out of engagement, the previously traced secondcircuit for energizing the motor is interrupted. Accordingly, this motoris deenergized and operation of the control device is arrested with thevarious cams occupying the positions illustrated in Fig. l of thedrawings.

Assuming that the connector switches 20 and 2| and the other similarswitches embodied in the system are of the calling party release type,when the call is cleared out at the calling substationv A the switches20, |18 and I4 included in the operated switch train are released in theorder named and in the manner previously eX- plained. When theconnection is cleared out at the called substation C, the back bridgerelay embodied in the connector switch 2| is caused to restore so thatthe direction of current flow over the loop circuit including the line'22, is again reversed. As a result, the polarized relay |30 restores toopen the loop circuit at its armature |3|. At its armature |32, therelay |30 opens the path short-circuiting the condenser |22. At itsarmature |33, the relay |30 reprepares the operating circuit for themotor III. When the loop circuit including the line 22 is thusinterrupted, the connector switch 2|, the selector switch I9 and theline switch 23 are successively released in the order named. Thus, theautomatic switching apparatus utilized in forwarding the connection tothe substation C is fully restored to normal.

1f, for any reason, the call as forwarded to the substation C is notanswered at this substation within the interval required lforthe'control device to complete its cycle of operation after the impulsetransmission is ended, the switch train through which the call isforwarded is released and a new cycle of operation of the control deviceis initiated; assuming that the call is not abandoned at the callingsubstation A during this interval. Thus, if the called line l2 is busyat the time it is selected by the connector switch 2 the connectionobviouslycannot be completed. In such case, the control apparatus of theconnector switch 2| functions to return busy tone over the loop circuitincluding the line 22 and extending to the repeating coil |23, in theusual manner. Since, however, no talking circuit is as yet establishedbetweenA the calling line I and the repeating coil |23, this busy signalis not transmitted to thev calling subscriber. lOn Athe contrary, theusual ring-back tone signal is transmitted to the calling substationcontinuously un-` til the call is abandoned or is successfullycompleted` Hence, it will be apparent that the calling party may notabandon the call for a substantialperiod, during which the controldevice of the call forwarding apparatus may operate through a number ofcycles. This may also occur in the case when the line to which the callis forwarded is idle, but the call as forwarded to the substationassociated with this line is` not answered promptly. In any event, whensuch a situation arises, the control device upon completing its firstcycle of operation interrupts, at the contact springs |34, the loopcircuit extending by wayof the line 22 to the line switch 23.

As a result7 the operated switch train comprising the switches 2|, I9and 23 is released. Since the start relay |20 is, underlthe conditionsas sumed, still operating intermittently in response to the ringingcurrent being transmitted over the line I the motor is deenergized onlyfor a short time interval, if at all, following the completion of thefirst cycle of operation of the control device. During the first ringingperiod following the end of the first cycle of operation of the controldevice, the relay |20 reoperates, the motor is again energized, and anew cycle of operation of the control device is initiated. From thispoint on, the manner in which the call is again forwarded to the calledsubstation C is exactly the same as explained above. A

In the event the call is abandoned at the calling substation A while acycle of operation of the control device is in progress and before thecall is answered at the substation C, the operated switch train throughwhich the'call is routed to the line is released, but the control deviceof the call forwarding apparatus continues to operate until the cycle ofoperation in progress is completed. Thus, so long as the contact springs|35 are engaged, the secondary circuit for energizing the motor is notinterrupted. Accordingly, if the call is abandoned while a cycle ofoperation of the control device is in progress, the control devicecontinues to operate. In such case, if the call is answered at thecalled substation C to cause the operation of the polarized relay |30 inthe manner previously explained, the called party is informed by thefailure of the calling party to respond to his answering salutation thatthe call has been abandoned, and may cause the operated switch trainthrough which the call is forwarded to the line |2 to be released byrestoring the receiver provided at the substation C to its supportinghook or cradle.

The call as routed to the line from the substation A may be answered atthe substation B even though the call forwarding apparatus isconditioned to operate in response to ringing current transmitted overthe line I. In such case, the ringing operation of the connector switch20 is arrested when the party answering the callremoves the receiverprovided at the substation B from its supporting hook or cradle toestablish a direct current bridge across the conductors of the lineSince operation ofthe control device is initiated when ringing currentis first transmitted over the line the call forwarding apparatusoperates to forward the call to the substation C. If the call isanswered at the last-mentioned substation before the control devicecompletes its cycle of operation, a three way connection is establishedbetween the substations A, B and C. Completion of the branch connectionto the substation C in no way interferes with the release of the callforwarding apparatus or the automatic switches through which theconnections are routed. s

Referring now more particularly to the embodiment of the call forwardingapparatus illustrated in Fig. 2 in association with the line I3extending tothe substation D, this apparatus includes a control devicewhich is substantially identical in construction and arrangement withthe corresponding device illustrated in Fig. 1 and included in the callforwarding apparatus associated with the substation B. For this reason,corresponding elements of the two control devices have been indicated inthe two iigures of the drawing by reference characters having the sametens and units digits but different hundreds digits. It will be notedthat the only difference between the two control devices is that in thearrangement illustrated in Fig. 2 the spring pile associated with thecontrol cam 208 comprises only two contact springs 236 and 238, whereasthe corresponding spring pile IID embodied in the control device shownin Fig. 1 includes an additional contact spring |31. In the Fig. 2arrangement, no auxiliary line between the substation arranged for callforwarding service and the central exchange switching apparatus isrequired, the switches utilized in forwarding a call from the line I3 toanother of the substations of the system being directively controlledthrough the provision of apparatus for transmitting over the line I3alternating'current impulses designating the substation to which thecall is to be forwarded. This apparatus, as provided at the substationD, comprises, in addition to the control device mentioned above, analternating current start relay 220 for initiating operation of thecontrol device and an alternating current relay 240 which is operativeto connect the conductors of the line I3 to an alternating currentpulsing circuit which includes a condenser 243 and the secondary windingof a voltage stepdown transformer 2M. This alternating pulsing circuitis arranged `to be controlled by the contact springs 2I0, 25| and 255 ofthe control device in the manner more fully explained subsequently.

For the purpose of repeating alternating current pulses transmitted fromthe substation D as direct current impulses over the line I3 to theautomatic switching apparatus provided in the line terminating exchange,there is provided in the exchange in association with this line aspecial line circuit 30. More particularly, the line I3 is divided atthe main distributing frame of the exchange into two normally connectedline sections |30 and |3d, the first of which extends to the substationD and the second of which extends to the automatic switching apparatusprovided in the exchange. Briefly described, the special line circuit 35comprises an alternating current relay which is normally bridged acrossthe conductors of the line section in series with a condenser 252 and isarranged to operate in response to ringing current transmitted over theline. The apparatus 3|] further comprises a slow-to-release hold relay255, a

switching relay 269, an alternating current pulsing relay 255, aslow-to-release line switching relay 21|) and a slow-to-release pulseresponsive relay 215. There is also provided a repeating coil 223 whichcorresponds to the repeating coil |23 of the Fig. 1 arrangement, and apolarized back bridge relay 230 of the permanent magnet type whichcorresponds to the back bridge relay embodied in circuits shown in Fig.l.

Referring now to the operation of the call forwarding apparatusillustrated in Fig. 2, it will be apparent that so long as the stationselecting element 202 of the control device occupies its normalposition, the alternating current relay 22|! is effectively disconnectedfrom the conductors of the line I3 and cannot respond to ringing currenttransmitted over this line. With the apparatus in this condition if acall originating at the substation A, for example, is forwarded by wayof the line Io, the line switch I4, the selector switch I9 and theconnector switch 2| to the line I3 at a time Vwhen the latter line isidle, ringing current is projected over the line I3 by the controlapparatus embodied in the connector switch 2| immediately following theoperation of this apparatus to determine the idleconditionof the line. Aportion of the ringing current traverses the Winding of the relay 250over a circuit which may partially be traced as extending by way of thearmature 21|, the armature 25|, the condenser 252, the winding of therelay 25|), the armature 262 and the armature 212. Each time this relayis energized by the ringing current it operates to complete, at itsarmature 25|, an obvious circuit for energizing the slow-to-release holdrelay 255. The relay 255, upon operating, prepares, at its armature 256,a circuit for energizing the relay 260. This latter circuit, whichextends by way of the armature 25 I, is completed at the end of eachringing interval in response to the release of the relay 255. Uponoperating, the relay 26|) connects the winding of the alternatingcurrent relay 265 across the conductors of the line I3 in series withthe condenser 261. Substantially simultaneously with the completion ofthe operating circuit for the relay 25|), the operating circuit for theslow-to-release relay 255 is interrupted. The period between ringingintervals is such that the relay 255 restores to cause the restorationof the relay 250 shortly following the end of each ringing interval andbefore the next ringingv interval occurs. Accordingly, the relays 250,255 and 26|) sequentially respond to each splash of ringing currenttransmitted over the line I3, but perform no useful function and do notfunction to cause the operation of any of the other relays embodied inthe line circuit 30. When the call is answered at the called substationD to cause the operation of the ring cut-off relay provided in theconnector switch 2 I, thereby to terminate the ringing operation, thethree relays 250, 255 and 260 are caused to restore. These relays remainin their respective restored positions until another call is routed tothe line I3.

If the call originating at the substation A is forwarded through theautomatic switches I4, I9 and 2| to the line I3 at a time when thestation selecting element occupies one of its offnormal positions, thecall forwarding apparatus illustrated in Fig. 2 operates to cause thecall to be forwarded to the substation corresponding to the off-normalposition occupied by the station selecting element. For example, if theelement 202 is set in the off-normal position corresponding tothesubstation B, the shunt springs 20| are positioned to be controlled bythe cam 200 and the contact springs 204 are engaged so that the relay220 is bridged across the conductors of the line |3. With the apparatusin this condition, if ringing current is projected over the line I3 therelays 250 and 255 are caused to operate in the manner explained above.In addition, the alternating current relay 22|! is energized by aportion of the ringing current, the circuit traversed by this currentextending by way of the armature 21|, the line conductor |3a, thearmature 242, the condenser 222, the winding of the relay 220, thecontact springs 204, the armature 2d I, the line conductor |31) and thearmature 212. When energized at the beginning of the first intervalduring which ringing current is transmitted over the line I3, the relay220 operates to complete, at its armature 22| and the associated workingcontact, a circuit for energizing the motor 2| I, this circuit extendingfrom one terminal of the alternating current supply source through thewindings of the motor 2I| andr -by way of the armature 22| to theopposite terminal of the current source. Operation of the motor is thusstarted toinitiate a cycle of operation of the control device. Duringthe initial rotary movement of the control cam 291 carried by the shaft2 I2, the springs 235 are closed to complete an obvious secondarycircuit for energizing the motor 2| I, whereby operation of the motor iscontinued after the release of the relay 226 at the end of the rstringing period. At the Contact springs 234 a circuit is prepared forconnecting the primary winding of the transformer 2M across theconductors of the alternating current supply source in parallel with thewinding of the alternating current relay 242. At the end of the firstringing interval, the relays 226 and 256 are deenergized and restore.The relay 256, upon restoring, completes the operating circuit for therelay 260, which latter relay in turn operates its armatures 26| and 262to connect the winding of the relay 265 across the conductors of theline section |30. Upon restoring, the relay 226 opens, at its armature22| and the associated working contact, the initially completed circuitfor energizing the motor 2||. At its armature 22| and the restingcontact associated therewith, the relay 220 completes theabove-mentioned circuit for energizing the relay 240 and the primarywinding of the transformer 264 in parallel. This circuit may be tracedas extending from one terminal of the alternating current supply sourceby way of the contact springs 235 to the armature 22| where it divides;one branch extending through the primary winding of the transformer 244and the contact springs 235 to the opposite terminal of the currentsupply source and the other branch extending by way of the condenser265, the winding of the relay 240 and the contact springs 235 to theopposite terminal of the current supply source. When energized over thiscircuit, the relay 256 operates to open, at the armatures 24| and 242and their respective associated'resting contacts, two points in theabove-traced circuit for energizing the relay 220. At these samearmatures and their respective associated working contacts, the relay246 completes the previously mentioned circuit for energizing thepulsing relay 265, this circuit extending from the upper terminal of thesecondary winding of the transformer 264 by way or" the armature 242,the line conductor |311, the armature 26|, the condenser 261', thewinding of the relay 265, the armature 262, the conductor |3b, thearmature 24|, the condenser 263 and the contact springs 2|!) to thelower terminal of the transformer secondary winding. Upon operating, therelay 265 completes, at its armature 266, a circuit for energizing theslow-to-release relay 216, this circuit extending from ground at thearmature 232 by way of the armature 266 and the winding of the relay 210to battery. At its armature 261, the relay 265 completes a calling loopcircuit including the repeater coil windings 226 and 221 and the windingof the polarized relay 236, and extending to the line switch 26. Therelay 210, upon operating, completes, at its armature 213, an obviousholding circuit for the relay 260, whereby the latter relay is heldenergized following the release of the relay 255 which occurs shortlyafter the operation of the relay 210. At its armatures 21| and 212, therelay 21D disconnects the line section |3d from the line section |3c,thereby to prevent the alternating current impulses transmitted over theline section |30 from being transmitted back over the calling end of theconnection. At these same armatures and their respective associatedworking contacts the relay'210 partially completes a connection betweenthe line section |3d and the repeater coil windings 224 and 225. At itsarmature 214, the relay 216 prepares a circuit for energizing theslow-to-release relay 215.

When the relay 265 operates to complete the above-mentioned loop circuitextending between the repeater coil 223 and the line switch 25, thisline switch operates to seize an idle one of the selector switches,such, for example, as the selector switch |8, and to extend the loopcircuit thereto. The direction of current flow over this loop circuit issuch that the polarized relay 236 does not operate at this time.Following the operation of the relay 216, the relays embodied in theline circuit 30 are conditioned to respond to alternating currentimpulses transmitted thereto from the substation D over the line |3. Inthis regard it is pointed out that the transmission of alternatingcurrent impulses to the line circuit 36 is delayed for an appreciabletime interval after the above-traced circuit is completed for energizingthe relay 265. This time interval is necessary in order to give the lineswitch 21| ample opportunity to select an idle one of the selectorswitches to which it has access. To this end, the spring 238 is held inengagement With its associated spring 236, to maintain the pulsingsprings 206 and the shunt springs 26| short circuited, during theinterval required for the cam 268 to rotate through an angle ofapproximately degrees corresponding to rotation of the cam 206 throughan angle of approximately degrees. At the end of this interval, the camfollower portion of the spring 238 drops into the notch 26311 formed inthe peripheral surface of the cam 268 so that the pulsing springs 266,as shunted by the shunt springs 26|, are actively included in theabove-traced circuit over which the pulsing relay 265 is energized. Themanner in which the pulsing springs 206 and the shunt springs 26|cooperate to interrupt this circuit in accordance with the impulses ofthe impulse digits determined by the respective lengths of the notches26M, 2666 and 266e is exactly the same as described above with referenceto the operation of the control device illustrated in Fig. 1. Thesenotches are formed of such lengths that the impulses of the directorynumber designating the substation B are transmitted over the linesection |30 to the pulsing relay 265. The relay 265, through operationof its armature 261, functions to repeat these impulses over the callingloop circuit to the automatic switching apparatus utilized in forwardingthe call. When the relay 265 restores at the beginning of the rstimpulse of each digit, it opens, at its armature 266, the above-tracedoperating circuit for the relay 216. At this same armature, the relay265 completes a circuit for energizing the slow-torelease relay 215,this circuit extending from ground by Way of the armatures 232, 266, 214and the winding of the relay 215 to battery. Upon operating at thebeginning of the first impulse of each digit, the relay 215 completes,at its armature 216, an obvious path for shortcircuiting the series pathincluding the winding 226, the winding of the polarized relay 236 andthe winding 221, thereby to exclude the impedance of these windings fromthe impulsing circuit over which the impulses are transmitted to theautomatic switching apparatus. Due to their slowto-releasecharacteristics, the relays 210 and 215 remain operated duringimpulsing. At the end of each digit the relay 265 is held operated for asuflicient time interval to permit the release of the relay 215, whichlatter, relay upon restoring,`V

nector switches having accessy to the` line II to.

which the call is to be forwarded. During the interdigit pause betweenrthe iirst and second digits, the selector switchv I3 operates to. seizean idle one of the connector' switches, such, for example, as the switch2.0.; in the selected group.

The seized.` connector switch 20 responds tothe impulses of the secondyand third digits by operating to select the line I'I in the exact mannerpreviously explained: with reference to the call' routed fromV thesubstation A to, the substation B.' Assuming that the line III is idleat the time it is selected; the control apparatus of the connectorswitch 20 operates to transmit ringing current over this linel for thepurpose of, energizing the signal device provided at the calledsubstation B. TheA arrangement of the control device located at thesubstation D is similar to the arrangement of the control deviceillustrated in Fig. 1 in that a substantial timeV interval elapsesbetween the end of the impulse transmission and the completion of thecycle of operation of the device.

positionls. This return movement` requires an angular rotation of thecams 201'and 208 of approximately 225 degrees, thus providing arelatively long time interval during which the substation By may besignaled and the call answered. Assuming that the call is answeredduring this interval, a loop circuit is established between the calledsubstation Band the connector switch 20, thereby to cause the operationof the ring cut-off and back bridge relaysembodied in this connectorswitch. The back bridge relay of the connector switch 20, uponoperating, reverses the direction of current flow over the loop circuitextending to the repeater vcoil 223 and including the winding of thepolarized relay 230. As a result, the relay 230 operates to complete, atits armature 233, an obvious path shunting the pulsing springscontrolled by the armature 2551 of the pulsing relay 255. At itsarmature 232, the relay 230 interrupts the operating circuit for therelay 210 andcompletes an obvious holding circuit therefor. At itsarmature 23I, the relay 230 completes a direct current path includingthe repeating coil windings 224 andy 225 across the line conductors ofthe line section ld. In response to this operation, the ring cut-oir"and back bridge relays embodied in the connector switch 2| are caused tooperate in the manner "f previously explained, thus completing thedesired talking circuit between the substation A and the substation B.

When the control device providedat the substation D completes its cycleof operation, the

More particularly, the cam follower portion of the spring 238 is movedout Iii motor 21| is deenergized and the two relays 240 and 265 arecaused to restore. More particularly, when the cam 201 is returnedto itshome position, the springs 234 and' 235 are respectively l disengaged toopen the secondary circuitv for energizing the motor 2II and theabove-traced circuit over which the winding of the relay 240 and theprimary winding of the transformerV 244 arey connected in parallelacross the alternating current supply source. Accordingly, thetransformer 244 is deenergizedv and operation of the motor 2II isarrested. When the relay 240 is.. deenergizedV it restores to open twopoints in the above-traced circuit for energizing the relay 2651 andreconnects the windin-g of the relay 22|)y The relay' acrossl theconductors of the line I3. 25.5, uponrestoring, opens, at its armature256, a furtherY point in the operating circuit for the relay 210 and, atits armature 261, opens thev path shunting the operated armature 233 ofthe back bridge relay 230.

The manner in which the connectionl as established between thesubstationsAand` B isrele'asedl is substantially similar to the releaseof the con- 5 nection established'through operation of the cally switchI8 to the connector switch 20 with the result that these switches arecaused sequentially to restore in the order named.y At its armature 232,the relay 230, upon restoring, opens the holding circuit for the relay210 causing the latter relay and the relay 250 sequentially to restore.At its armature 23I., the relay 230 opens a point in the loop circuitextending t'o the con-- nector switch 2I. Thus, the callforwarding-apparatus illustrated in Fig. 2 isfully restored to normal.

The arrangement of the call' forwarding apparatus shown in Fig. 2 issimilar to thearrangement of the apparatus illustrated in Fig. k1 inthat a callextended to the line I3 is repeatedly forwarded to thesubstation designated by the setting of the element 202 throughrepeatedoperations of the control device provided. at the substation Duntil the call is answered or is abandoned at the calling substation.More particularly, if the call as forwarded to the substation B is notanswered during the interval which elapses between the end of the lastseries of impulses transmitted over the line I3 and the end of the cycleof operation of the control device, the switch train through which thecall is for,- warded to the substation B is released. Thus, when the cam201 is returned to its home position the contact springs 234 and 235 arerespectively disengaged so that the relays 240 and 265v are caused torestore rin the manner previously explained. Under thecircumstancesdescribed, the back bridge relay 230 is not operated.Accordingly, the relay 265, upon restoring, interrupts the operatingcircuit for. the relay 210, causing the relays 210 and V250 sequentiallyto restore. At its armature 261, the relay 265, upon restoring, alsointerrupts the loop circuit extending byy-l way of the, line switch 24and the selector `switch I8 to the operated connector switch 20. Inresponse to this operation, the switches 20, I3 and 24are causedsequentially to restore in the order named,

thus releasing the connection over which the call was initiallyforwarded to the substation B. If required, the relay 210 may beequipped with a dash pot or other suitable release retarding device inorder to prevent the release of this relay before the switches 20, I8and 24 are fully released. This release retarding device should be ofsuch type that the relay 210 is fast-to-operate when energized. Therelay 210, upon restoring, reconnects the line section I3d to the linesection I3c so that if the call has not been abandoned, ringing currentis again transmitted over the line section I3c to cause lthe reoperationof the two relays 250 and 220. Hence, a new cycle of operation of thecontrol device is initiated. From this point on, the manner in which thecall is again forwarded through the automatic switching apparatus to thesubstation B is exactly the same as described above.

If the call is abandoned at the calling substation A during a cycle ofoperation of the control device provided at the substation D, thisdevice continues to operate until the cycle of operation is ended, afterwhich the call forwarding apparatus is released. In this regard, it willbe apparent that if the call is abandoned while the control device is inoperation and the call is then answered at the substation B during thelast part of the operating cycle of the control device, the answeringparty will be informed by the failure of the calling party to answer,that the call has been abandoned and may then condition the apparatus tobe released at the end of the cycle of operation of the control deviceby restoring his receiver to its supporting hook or cradle. In the eventthe cycle of operation of the control device is completed before theanswering party hangs up, the manner in which the three relays 23D, 210and 260, embodied in the line circuit 30, are released when theconnection is cleared out at substation B is exactly the same asdescribed above. In the event the call is not answered or is answeredand released after the call is abandoned but before the cycle ofoperation of the control device is ended, the call forwarding apparatusis restored to normal linmediately the cam 201 is returned to its homeposition. In response to this operation, the motor 2| I, the relay 240and the transformer 2M,A are all Vdeenergized in the manner set forthabove. In addition, the 'relay' 265 -is caused to restore to interruptthe loop circuit extending through the line switch 24 and to open theoperating circuit for the relay 210. Thus, the relays 210 vand 260 arecaused sequentially to restore and the switch train through which thecall was forwarded to the line II is released. With' the arrangementillustrated in Fig. 2, a call routed to the line I3 from another line ofthe system cannot be answered at the substation D if the call forwardingapparatusA is conditioned for operation. Thus, immediately after the rstinterval during which ringing current is projected over the line I3 therelay 21|! is caused to operate to disconnect the line section I3d fromthe line section I3c. Hence, ringing current is only transmitted overthe line sectionv I 3c for one short interval and no talking circuit canbe completed between the substation D and the connector switch throughwhich the connection is routed to the line I3.

While there has been described what are at present considered to be thepreferred embodiments of the invention, it will be understood thatvarious modications may be made therein, and

it is contemplated to cover in the appended claims all suchmodifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In an automatic telephone system including a plurality ofvsubstations and means comprising automatic switching apparatus forsetting up connections between said substations, a line extending to oneof said substations, said automatic switching apparatus includingaconnector switch operative to seize said line and to transmit ringingcurrent thereover in routing a call to said one substation, callforwarding apparatus associated with said one line and operativedirectively to control said automatic switching apparatus to route acall incoming to said line through said automatic switching apparatus toany one of a plurality of other substations, means responsive to ringingcurrent transmitted over said line for initiating the operation of saidapparatus, and means operative in response to the answering of said callat said other substation for terminating the ringing operation of saidconnector switch.

2. In an automatic telephone system including a plurality of substationsand means comprising automatic switching apparatus for setting upconnections between said substations, a line extending to one of saidsubstations, said automatic switching apparatus including a connectorswitch operative to seize said line and to transmit ringing currentthereover in routing a call to said one substation, call forwardingapparatus comprising a cyclically operative device associated with saidline and operative to transmit to said automatic switching apparatus theimpulses of the directory number designating another of saidsubstations, a motor for driving said device, means responsive toringing current transmitted over said line for initiating the operationof said motor, means responsive to the initial operation of said devicefor maintaining the operation of said motor until the cycle of operationof said device is completed, said automatic switching apparatusincluding automatic switches operative to extend a connection from saidline to said other substation in response to the impulses transmittedthereto from said device, and means operative to terminate the ringingoperation of said connector switch when the call forwarded to said othersubstation over said last-named connection is answered.

3. In an automatic telephone system including a plurality of substationsand means comprising impulse responsive automatic switching apparatusfor setting up connections between said substations, a line extending toone of said substations, a relay adapted to bev bridged across theconductors of said line to respond to ringing current transmitted tosaid one substation on calls incoming thereto, call forwarding apparatuscomprising a cyclically operative device associated with said line andoperative to transmit to said automatic switching apparatus the impulsesof the directory number designating another of said substations, a motorfor driving said device, a first circuit for energizing said motor, saidfirst circuit being completed in response to operation of said relay, asecond circuit for energizing said motor, said second circuit beingcompleted in response to the initial operation of said device, saidautomatic switching apparatus including automatic switches operative toextend a connection from said one line to said other substation inresponse to the impulses transmitted thereto from said', device, meansvoperative to interrupt said first circuit when the call forwarded tosaid other substation oversaidrlastnamed connection isanswered, and.means 'con'- trolled by said device for interrupting said second circuitafter said device has completed a.

cycle of operation.

4. In an automatic telephone system including a plurality of substationsand means comprising impulse responsive automatic switching apparatusfor setting up connections between saidsubstations, a line extending toone ofsaid substations, a relay and a condenser connectedv in series andadapted to be bridged across the conductors of said line,whereby-saidrrelay responds to ringing current transmitted to said;

substation on calls incoming to said onel substation, said automaticswitching apparatus including a connector switch operative to seize saidline and to transmit ringing current thereover in routing a call to saidone substation; call for.`

said motor, said iirst circuit being completed in response to operationof said relay, a second circuit'for energizing said motor, said secondcir-- cuit being completed in response to the initial operation of saiddevice, saidautomatic switching apparatus includingautomatic'sWitches-operative to extend a connection from said linetorsaid other substation in response to the impulses.

transmitted thereto from said device, means-op'- erative toshort-circuit said condenser, thereby to cause the ringing operation ofsaid connector switch to .be terminated and also operative tov interruptsaid rst circuit when the call forwarded to said other substation oversaid lastnamed connection is answered, and means controlled by saiddevice for interrupting said second circuit after said device hascompleted a cycle of operation.

5. In an automatic telephone system-` including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, callforwarding apparatus comprising a cyclically operative deviceassociatedl with one of said substations and operative tothe operationof said motor until the cycle ofv operation of said device is ended,said automatic switching apparatus including automaticA switchesoperative to extend a connection to said` other substation in responseto the impulsesl transmitted thereto from said device, and, saidVcontrol elements being so constructed, andl arranged that said switchesare held operated for' an interval after said impulse transmission isended. k

6. In an automatic telephone system including a plurality of substationsand means comprising impulse responsive automatic switching appara tusfor setting up connections between saidsubi impulse responsive-automaticswitching apparastations,A call` forwarding apparatus comprising acyclically'operative device associated with one l of said substationsand operative .to transmit to said automatic .switching apparatus theimpulses ,l of the directory number designating ano-ther of saidsubstations, saidA device including an impulsingcontrol element and aswitch release control element, Aa motor for driving said. device, meansresponsive to a: call route-d to said one substation forinitiating theoperation of said motor, and means controlled'by said switch releasecontrol' element for; maintaining the operation of said motor untilthe.cycle of operation of said device is ended, said automatic switchingapparatus including automatic switches operative to extend a connectionto said other substation in .response tothe impulses transmitted theretofrom said device,.said control 'elements being. so. constructed andarranged that said switches are held, operated for an interval aftersaid impulse. transmission is ended, and means operativein thev eventthe .call as forwardedv to said'. other substation over said last-namedconnection-is answered during said interval for holding: said switchesoperated independently of said device:

7. Inv anautomatic telephone systemincluding a` plurality ofsubstationsandmeans comprising impulse responsive automatic switchingapparatusifor setting-up connectionsbetween said substations, callforwarding apparatus comprising a` devicefprovided att onezof saidsubstations and including a plurality of control elements individuallycorresponding to certain of the other .isubstations of said system, astation selecting element having a normalposition and operative tooit-normal positions individuallyy corresponding'tosaid controlelements, and pulsing means adapted toV becontrolled by. any one of saidcontrol elements for transmitting to said` automatic switching apparatusthe impulses of the directoryf. number designating" the substationcorresponding tov thef oni-normal position occupied by said stationselectingelement, a motor forl driving said device, a devicefor-'initiating the operation of said motor, and'means responsive tooperationof said station selecting element to any one of said ofi-normalpositions for` conditioning. said last-named device to operate inresponse toa call. routed to said one substation.

8; In an automatic telephone system including a plurality of substationsand means comprising tus forsettingup connections between saidsubstations, aline extending to one of said substations, call forwardingapparatus comprising ay device provided at said one substation andincluding a plurality of control elements individually corresponding tocertain of the other substations ofthe system, a station selectingelement having a normal position and operative to offnormal positionsindividually corresponding to saidicontrolelements, and pulsing meansadapted. to be controlled by any one of said control elements fortransmitting to said automatic switching apparatus the impulsesjof thedirectory numberV designating the substation corresponding to theoir-normal position occupied by said station selecting'element, a motorfor driving said i device, a relay adaptedtovvbe bridged -across theconductors of said line to respond to ringing currenttransmitted oversaid line, a circuit for energizingsaidmotor, means controlled by saidrelayfor completing said circuit, and means operative tobridge saidrelay across the conducstation selecting element to oneOfsaid'oif-normal-positions. 9. In an automatic telephonesystemincluding a plurality of substations and means comprising impulseresponsive automatic switching apparatus for setting up connectionsbetween said substations, a line extending to one of said substations,call forwardingapparatus comprising a cyclically operative deviceprovided at said one substation and includinga plurality of controlelements individually corresponding to certain of the other substationsof the system, a station selecting element having a normal position andoperative to oir-normal positions individually corresponding to saidcontrol elements, and pulsing means adapted to be controlled by any oneof said control elements for transmitting to said automatic switchingapparatus the impulses of the directory number designating thesubstation corresponding to the off-normal position occupied by saidstation selecting element, a motor for driving said device, a relayadapted to be bridged across the conductors of said line to respond toringing current transmitted over said line, a circuit for energizingsaid motor, means controlled by said relay for completing said circuit,means operativeto bridge said relay across the conductors of said linein response to operation of said station selecting element to one ofsaid off-normal positions, a second circuit for energizing said motor,and means operated during the initial operation of said device forcompleting said second circuit and for maintaining said second circuitcompleted until the cycle of operation ofsaid device is ended.

10. In an automatic telephone system, a plurality of substations, meanscomprising automatic switching apparatus for setting up connectionsbetween said substations, a line extending to one of said substations,and call forwarding apparatus comprising means automatically operativewhen an incoming call is present on said one line for repeatedlyforwarding said call through said automatic switchingapparatus toanother of said substations until said call is abandoned or is answeredat said other substation. i

1l. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineextending to one of said substations, call forwarding apparatuscomprising a cyclically operating device for transmitting to saidautomatic switching apparatus the impulses of the directory numberdesignating another of said substations during each cycle of operationthereof, and means operative when an incoming call is present on saidone line for causing said device to operate through repeated cycles,thereby repeatedly to forward said call to said other substation, untilsaid call is abandoned or is answered at said other substation.

12. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineextending between said automatic switching apparatus and one of saidsubstations, call forwarding means comprising apparatus operative tocause a connection to be extended from said line through said automaticswitching apparatus to another of said substator's of said line inresponse to operation of said' tions in response to Aalternating currentimpulses' transmitted thereto, and means automatically operative inresponse to the presence of anincoming call on said line fortransmitting alternating current pulses to said last-mentionedapparatus.

13. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineextending between said automatic switching apparatus and one of saidAsubstations, call forwarding apparatus comprising an impulsing deviceat .one of saidv substations,' i means controlled by said device'fortransmitting over said line alternating current impulses correspondingto the directory number designating another of said substations,apparatus operative in response to said'alternating current impulses forcausing a connection to be extended from said line through saidautomatic switching apparatus to said other substation, a motor fordriving said device, and means operative in response to the presence ofvan incoming call onV said line for initiating the operation of saidmotor.

14. In an automatic telephone system including a plurality ofsubstations and -means comprising impulse kresponsive automaticswitching apparatus for setting up connections between said substations,a line extending between said automatic switching apparatus and one ofsaid substations, call forwarding apparatus comprising an impulsingdevice at 'one of said stations;

said impulsing device including a plurality of control elementsindividually corresponding to certain of the other substations of thesystem, a station selecting element having a normal position andloperative to' off-normal positions individually corresponding to saidcontrol elements,

and means for transmitting over said line alternating current impulsesdesignating the substation corresponding to the OIT-normal positionoccupied by said station selecting element; apparatus operative inresponse to said'alternating cur'- rent impulses for causinga connection'to be extended from said line through said automatic switchingapparatus to the substation designated by theposition occupied by saidstation selecting element, a motor for driving said device, a circuitfor energizing said motor, a device operative to complete said'circuit,and means'responsive to operation of said stationv selecting element toone of said off-normal positions for conditioning saidV last-nameddevice to operate in response to a call routed `to said one substation.

15. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between' said substations, a lineextending from said automatic switching apparatus to one of saidsubstations, call forwarding apparatus comprising a device operative inresponse to ringing current transmitted over said line, 'meanscontrolled by said device for transmitting over said line alongalternating current pulse followed by alternating current impulsescorresponding to the directory number designating another of saidsubstations, a pulsing relay adapted to be connected to said line torespond to said alternating current pulses and to repeat said impulsesto said automatic switching apparatus, thereby to extend a connectionfrom said line through said automatic switching apparatus to said othersubstation, and means controlled by ringing current transmitted oversaid line for connecting said pulsing relay to said line.

16. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineextending from said automatic switching apparatus to one of saidsubstations, a repeater including a rst winding adapted to be connectedacross said line and a second winding adapted to be included in acalling loop circuit extending to said automatic switching apparatus,call forwarding apparatus comprising a device operative in response toringing current transmitted over said line, means controlled by saiddevice for transmitting over said line a long alternating current pulsefollowed by alternating current impulses corresponding to the directorynumber designating another of said substations, a pulsing relay adaptedto be connected to said line to respond to said alternating currentpulses, said pulsing relay being operative to complete said calling loopcircuit and to repeat said impulses by way thereof to said automaticswitching apparatus, whereby a connection is routed from said repeaterthrough said automatic switching apparatus to said other substation,means responsive to operation of said pulsing relay for connecting saidfirst winding t said line, and means controlled by ringing currenttransmitted over said line for connecting said pulsing relay to saidline.

17. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineextending from said automatic switching apparatus to one of saidsubstations, a repeater including a first winding adapted to beconnected across said line and a second winding adapted to be includedin a calling loop circuit extending to said automatic switchingapparatus, call forwarding apparatus comprising a device operative inresponse to ringing current transmitted over said line, means controlledby said device for transmitting over said line a long alternatingcurrent pulse followed by alternating current impulses corresponding tothe directory number designating another of said substations, a pulsingrelay adapted to be connected to said line to respond to saidalternating current pulses, said pulsing relay including contacts forcompleting said loop circuit and for repeating said impulses by way ofsaid loop circuit to said automatic switching apparatus, whereby aconnection is routed from said repeater through said automatic switchingapparatus to said other substation, a hold'relay operative to connectsaid first winding to said line in response to operation of said pulsingrelay, a holding circuit for said hold relay, means controlled byringing current transmitted over said line for connecting said pulsingrelay to said line, and means operative when the call forwarded to saidother substation is answered for completing said holding circuit and forshunting sai pulsing contacts.

18. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineincluding two normally connected sections, one of said sectionsextending to said automatic switching apparatus and the other of saidsections extending to one of said substations, a repeater including afirst winding adapted to be connected to said one line y section and asecond winding adapted to be included in a calling loop circuitextending to said automatic switching apparatus, call forwardingapparatus comprising a device operative in response to ringing currenttransmitted over said line, means controlled by said device fortransmitting over said other line section a relatively long alternatingcurrent pulse followed by alternating current impulses corresponding tothe directory number designating another of said substations, a pulsingrelay adapted to be connected to said other line section to respond tosaid alternating current pulses, means controlled by said pulsing relayfor completing saidy calling loop circuit and for repeating saidimpulses by way of said calling loop circuit to said automatic switchingapparatus, whereby a connection is routed from said repeaterl throughsaid `automatic switching apparatus to said other substation, meansresponsive to operation of said pulsing relay for disconnecting said oneline section from said other line section and for connecting said oneline section to said rst winding, and means controlled by ringingcurrent transmitted over said line for connecting said pulsing relay tosaid other line section.

19. In an automatic telephone system including a plurality ofsubstations and means comprising impulse responsive automatic switchingapparatus for setting up connections between said substations, a lineincluding two normally connected sections-one of said sections extendingto said automatic switching apparatus and the other of said sectionsextending to one of said substations, a repeater including a rst windingadapted to be connected to said one line section and a second windingadapted to be included in a calling loop circuit extending to saidautomatic switching apparatus, call forwarding apparatus comprising adevice operative in response to ringing current transmitted over saidline, means controlled by said device for transmitting over said otherline section a relatively l'ong alternating current pulse followed byalternating current impulses corresponding to the directory numberdesignating another of said substations, a pulsing relay adapted to beconnected to said other line section to respond to said alternatingcurrent pulses, said pulsing relay including contacts for completingsaid loop circuit and for repeating said impulses by way of said callingloop circuit to said automatic switching apparatus, whereby a connectionis extended from said repeater through said automatic switchingapparatus to said other substation, a hold relay operative to prepare aconnection between said one line section and said rst winding inresponse to operation of said pulsing relay, a holding circuit for saidhold relay, means controlled by ringing current transmitted over saidline for connecting said pulsing relay to said other line section, andmeans loperative. when the call forwarded to said other substation isanswered for completing said last-mentioned connection, completing saidholding circuit and shunting said pulsing contacts.

JOHN WICKS.

